The present invention relates generally to a robotic system for processing an article in serial high-volume production. More particularly, the invention pertains to minimizing the size of a painting booth containing a robotic system used to paint a motor vehicle body.
The safety zone is an area in a painting booth where people could be present while a robot, mounted for movement along a rail beside a conveyor, operates. Frequently people are present in the booth to view the robot in operation. It is conventional practice to use a limit switch, mounted on the rail, to stop the robot at a fixed location on the rail and prevent an articulating robot arm from entering the safety zone located at the end of the rail. If the robot travels too far down the rail, it will trip the limit switch and cause the robot to stop before the arm enters the safety zone.
Other techniques have been employed to guard against personal injury caused by a robot operating in a painting booth. For example, a light curtain, located at the boundary of the safety zone, stops the robot from entering the safety zone when the curtain is crossed by the end of the robot arm or tooling carried by the arm. The light curtain reduces the length of the rail and paint booth because it allows the robot to move to the end of the rail provided it does not cross the light curtain.
In an automotive paint booth, it is conventional to use a silhouette or cattle fence between the safety zone and the robot. The silhouette is a wall with a cutout slightly larger then the envelope of the vehicle body being process in the booth. The cattle fence is a railing that partially isolates the safety zone from the robot-painting zone. The cattle fence extends from the sidewall of the booth into the booth. There is an opening in the middle of the cattle fence that allows vehicle bodies to pass through the fence.
These devices are awareness barriers to remind people to stay out of the working range of the robot rather then a wall that is designed stop the robot. The light curtain typically extends from one side of the booth to the other side. But the light curtain must be disabled when the vehicle body is present because the vehicle body would otherwise break the light beam as the body passes along the conveyor path. Therefore, a control system is required to disable the light curtain, when the vehicle body passes through the light curtain. However, paint booth operators prefer that a safety emergency stop system operate independently of a control system, which, if operating correctly, would prevent the robot from entering the safety zone. Once the light curtain is disabled to allow the vehicle body to pass through the curtain boundary, booth occupants would not be protected from the robot if it went out of control and passed through the silhouette or cattle fence.
The limit switch wastes rail and booth line length. The light curtain must rely on a control system to disable the curtain when a vehicle body passes through the curtain boundary. When the light curtain is disabled to allow a vehicle body to pass, it doesn't offer any protection to a person in the safety zone. If control of the robot is lost while the curtain is disabled, the robot could pass through the silhouette or cattle fence undetected and enter the safety zone.
A technique is required that avoids wasted rail and booth length preferably by synchronizing the trip point of a limit switch based on the position of the rail and the angle of articulation of the robot the waist.
Other methods to reduce the size of a robotic paint booth and improve paint booth process throughput are required. For example, a painting robot, door opener robot, and a hood/deck opener robot, mounted on rails in the paint booth, would operate more efficiently if they could pass each other on the rails while performing their respective tasks.
Space in the paint booth that is required to accommodate direct charge atomizers could be saved by using a paint applicator, such as a rotary atomizer, that ionizes a stream of air directed onto the atomized paint produced by the atomizer.
A method to isolate a nonconductive paint component from a conductive component before mixing them is required when using a direct charge electrostatic application, in which the fluid stream is charged via direct contact with a high voltage probe.
paint utility line failures are costly and time consuming to repair. It is necessary to support paint system utility lines connected across an articulating joint of a robot arm against failure induced by flexing the lines as the arm articulates. An arrangement of the utility lines that minimizes flexural displacement is required.
A goal of automatic painting equipment is to change rapidly from one paint color to another. Often the painting equipment includes a dump circuit, fluid passages used to carry cleaning solvent and waste paint from the system, as a means for venting existing air in the system before paint flow starts. It is preferable that a dump circuit for the solvent and waste paint land, and a vent circuit for venting air would be arranged for coordinated operation in order to expedite a cleaning operating, in which lines and operating components are cleaned and flushed of waste paint and solvent, and a color change operation, in which the system is filled with a new paint color.